Comparative Analysis of Refractive Index Mapping of 3D Printed Polymeric Optics Using Raman Microscopy and Interferometry

Using the correlation between conversion and a refractive index as well as a model for controlling the extent of cure, the refractive index can be tailored to 3D printed polymeric graded index optics. As with any emerging technology, additional methods for characterization arise. While attenuated total internal reflection infrared (ATR-IR) microscopy has proven to be beneficial in this endeavor, the low spatial resolution alongside the need for surface contact limits the measurement capabilities and often damages the components, rendering them useless. Raman microscopy, however, offers a noncontact method to spatially map the chemical conversion, thus preserving the sample for further analysis and use. In this work, we produce a two-dimensional index of refraction profiles for graded index optics based on monomer-to-polymer conversion. These 3D printed graded index components were then compared with the predicted values based on the printing model using Raman microscopy and Mach–Zehnder interferometry. This work not only demonstrates the efficacy of using Raman spectroscopy for the index of refraction mapping through comparative analysis but also provides a pathway toward the noncontact 3D index of refraction mapping of freeform graded index optics.